1. Field of the Invention
The present invention relates to a base plate for use of a recording head for printing on a recording medium, which has an energy converting element to discharge ink by generating a bubble in ink with the conversion of electric energy to thermal energy. The invention also relates to a method for manufacturing such recording head. More particularly, the invention relates to a base plate for use of a recording head, which is a semiconductor base plate having a printing energy generating element and others formed thereon to generate printing energy, and also, relates to the method of manufacture therefor.
Here, it is to be understood that the printing on a recording medium contains not only the printing operation of characters, but also, contains the printing operation of those other than characters, such as symbols, figures.
2. Related Background Art
There has been known conventionally the ink jet recording method, that is, the so-called bubble jet recording method, in which change of states accompanied by abrupt voluminal changes in ink (generation of bubble) is created by giving energy, such as heat, to ink or other liquid, and ink is discharged from a discharge port by acting force exerted by this change of states, and then, ink thus discharged is allowed to adhere to the recording medium for the formation of images. For a recording apparatus that uses this bubble jet recording method, there are generally arranged a discharge port for discharging ink, an ink flow path communicated with the discharge port, and heat generating resistive member provided in the ink flow path as an energy converting element for discharging ink as disclosed in the specification of U.S Pat. No. 4,723,129, and others.
The recording method of the kind makes it possible to record high-quality images at high speed with a lesser amount of noises, while the discharge ports for discharging ink for the head that records using such method can be arranged in high density. As a result, it becomes possible to make the apparatus smaller and obtain recording images in high resolution, and even in colors with ease, among many other excellent advantages of the method. In recent years, therefore, the bubble jet recording method has been utilized for a printer, a copying machine, facsimile device, and many other office equipment. Further, this method has been utilized even for industrial systems, such as textile printing system.
Further, in recent years, in order to detect the presence of ink and the like, a method has been used for detecting the presence and absence of ink by applying electric signal to ink. For example, in the specification of Japanese Patent Application Laid-Open No. 7-60953, a structure is disclosed, in which an anti-cavitation film is used as electrodes for applying electric signal to ink, and with the electrodes provided for an ink tank for use of ink absence detection, the presence or absence of ink is detected depending on whether or not such electric signal is detected.
Now, however, the printing width of a head, that is, the number of nozzles, has been increased greatly in order to implement higher-speed printing in recent years. Along with this, heat generated on the head has been increasingly made higher year after year, and the countermeasure against the heat thus increased is of an important aspect to be overcome. As one of solutions therefor, there is a technique in which the protection film provided for the heater is made thinner so as to enhance the heat conductivity from the heater to ink for obtaining a higher bubbling efficiency.
As described earlier, on the other hand, there is introduced such technique as to apply voltage pulses to ink with the anti-cavitation film formed by metallic film, such as Ta, being arranged as electrodes for the detection of ink status. The resultant structure is then such that the terminals connected directly with the anti-cavitation film are exposed on the head contact portion.
Behind such technical aspect, there has been an event that with the conventional protection film in a thickness of (5,000 Å to 10,000 Å), it is possible to effectuate covering by use of such protection film even when static electricity is charged in a state that the terminals electrically connected to the anti-cavitation film directly are exposed on the head contact as described above. However, in a structure where the protection film is made thinner (in a thickness of less than 5,000 Å or preferably, less than 3,000 Å) to enhance the discharge efficiency of the heater, dielectric breakdown takes place between the insulated circuit on the element substrate and the anti-cavitation on the stepped portion of wiring, such as AL, where the covering effect of the protection film becomes weaker particularly on the base plate for use of the recording head, for which the circuit for heater and others are formed. This is confirmed as a problem that leads to defective printing.
Also, it is confirmed that dielectric breakdown takes place by the application of static electricity in the resistor for use of monitoring resistance values (rank resistance), as well as in the sub-heater used for keeping the element substrate warm, which may lead to defective operation. In a case of the base plate for use of an ink jet recording head, the anti-cavitation film is provided through a protection film for the logic element substrate or the like, which is weaker against impurities. Then the structure is arranged so that the ink that contains a considerable amount of ion is present thereon, which easily damages semiconductor. Here, the inventors hereof have recognized that in such particular structure of the base plate for use of an ink jet recording head, the countermeasure against static electricity is extremely important when the protection film should be made thinner.
Here, the place where static electricity escapes is considered to be the base portion of the silicon semiconductor base plate, which has the largest volume, and characteristics common to the aforesaid anti-cavitation film, rank resistance, and sub-heater are such that static electricity is concentrated on the place, such as the anti-cavitation film, through which the pressure tends to escape to the base portion against the high voltage of static electricity, but withstood by the insulation of the protection film or concentrated on the rank resistance and sub-heater where the high-voltage that escapes to the base portion is gradually eased by the resistance thereof against it.